Large-scale generation of electric power from solar energy continues progressing as an attractive modality for clean and efficient generation of electric power, such as may be generated from a freely-available and essentially inexhaustible source of energy, the Sun.
In the case of direct conversion of solar radiation to electricity, the solar-based power generation system may include a solar (e.g., a photovoltaic (PV)) array, which is a linked collection of solar modules. A solar module in turn is made-up of multiple interconnected solar cells or so-called strings. The cells directly convert solar energy into direct current (DC) electricity via the photovoltaic effect.
The output power of a solar module is approximately proportional to the level of solar irradiance to which the module is exposed. It will be appreciated, that in certain applications, such as solar power plants, building-integrated PV systems, etc., the photovoltaic modules may be subject to non-uniform solar illumination or so-called radiation. Possible causes of non-uniform solar radiation may be solar radiance obscuration (e.g., shadows) due to clouds, neighboring trees and/or man-made structures, soiling, etc. Regardless of the specific cause, shadowing of a solar module may result in a degraded performance of the module. For example, the characteristics of the current-voltage (I-V) and power-voltage (P-V) curves of the solar module may be substantially affected by the level of solar irradiance to which the module is exposed. Moreover, a shadowed solar cell could be detrimentally affected since a shadowed cell may behave like a load (i.e., it may draw current), which could lead to the formation of undesirable hot spots. It will be appreciated that suboptimal performance resulting from shadows is not limited to systems involving direct-conversion components. For example, indirect-conversion systems involving components, such as solar collectors may also be affected by the presence of shadows.
It is known to use pyranometers for measuring solar radiance. Pyranometers are thermally-responsive devices, and consequently may be relatively sluggish in their response. For example, pyranometers may not be suitable for accurately detecting rapid solar radiance fluctuations, such as may occur due to moving clouds. It is also known to use PV sensors for measuring solar radiance. A PV sensor may consist of a solar cell, whose output power may be dependent on the operating temperature of the solar cell, which means that temperature sensing may be needed to offset thermal effects. Additionally, although PV sensors may have a faster response than pyranometers, PV sensors tend to be less accurate in their measurements than pyranometers.
In view of the foregoing considerations, it would be desirable to provide a reliable, accurate, relatively fast-response and low-cost apparatus to determine a presence of shadows in solar-based power generation systems.